Conventional field tractors with unsprung wheels no longer meet the demands for higher travel speed in road traffic, greater efficiency and economic soil conditioning in field operation whilst at the same time providing the best possible driving comfort. One precondition for achieving this is a vehicle suspension with the lowest possible unsprung mass. Field tractors with a rigid axle body between the wheels, as described in DE 201 06 172 U1 and EP 0 494 286 Bi, are poorly suited for meeting the requirements mentioned because of the high mass compared to that of the wheels. Moreover, the fact that the rear axle, uncoupled from the gearbox, is driven by a cardan shaft which departs from the vehicle gear, gives rise to a larger wheelbase which in turn results in a larger turning circle, thereby reducing the maneuverability of the vehicle. In the light of this it would appear appropriate, in the case of field tractors, to dispense with a rigid axle, at least in the rear area, and to adopt a single wheel suspension of the wheels.
Independent suspension for the wheels of field tractors is known. For example, a sprung support for the driven wheels of such vehicles is described in DE-PS 484 552: A wheel shaft departing from a universal joint in the gearbox extends through an axle housing secured to the side of the gearbox and supports a wheel at its free end. In the region of the wheel the axle housing passes into a vertical, arch-shaped guide in which a bearing, also arch-shaped and supported on the wheel joint, is guided so that the wheel shaft, with the wheel, is able to swivel about the universal shaft against the force of leaf springs in the manner of transverse swinging arm. This design is relatively complicated.
A further independent suspension for wheels of field tractors, in which a wheel support is guided by means of several transverse swinging arms, was presented by the company John Deere at AGRITECHTNICA, which was held in Hanover, Germany in November 2001. However, the three transverse swinging arms and the cardan shaft driving the wheel are fully unprotected and therefore require a high degree of maintenance.